[fpc-pascal] Fast CRC functions?

[Marco van de Voort]

In our previous episode, Michael Schnell said:
> More characteristics that can be differ in certain applications are
> - bit count
> - starting value
> - shift count (only data block bits or data block bits plus CRC bits
 - Shift direction. msbit first, lsbit first, in case of wordwise crc also
   low/hi byte.
 - in case of (d)wordwise CRCs padding value.
> - order of the bits (including bits in bytes and/or words), as well in 
> the data block as in the CRC itself
> - sometimes the data bits are inverted before the CRC calculation, 
> sometimes the CRC bits are inverted before transmission.